Traces of another world found on the Moon. Researchers have found evidence of the world that crashed into the Earth billions of years ago to form the Moon. Analysis of lunar rock brought back by Apollo astronauts shows traces of the "planet" called Theia.
Collision Between Two Planetary Bodies. A similar crash likely formed the Earth and the Moon some billion years ago. The newly formed Earth may have taken most of the water and other volatiles remaining after the collision.